Organ vibrato control



Jan. 22, 1963 R. E. WILLIAMS 3,

ORGAN VIBRATO CONTROL Filed Sept. 8, 1959 INVENTOR Ava/M 0 z: n xw/wxs,

United States Patent 3,074,305 ORGAN VIBRATD CONTROL Richard E. Williams, Fairfax, Va., assignor to Scope, Inc, Fairfax, Va., a corporation of New Hampshire Filed Sept. 8, 1959, Ser. No. 838,762 3 Claims. (Cl. 84-115) This invention relates to an organ vibrato control, and more particularly to simplified arrangement for providing a variable vibrato in electric and electronic organs which utilize moving tone wheel generators.

Musical tones have two basic properties, loudness and pitch. It is possible to embellish or enhance the aesthetic efiect of a musical tone by periodically varying either the loudness (amplitude) or the pitch (frequency) of the tone rapidly and between fixed limits. In musical terminology the loudness or amplitude variation is known as tremolo, While the pitch or frequency variation is known as vibrato.

In many musical instruments, as well as the voice itself, it is considered desirable at times to introduce a certain amount of vibrato. A common example of this in a hand instrument is found in the playing of the violin where the musician introduces a pitch or frequency variation in tone by varying the position of his finger on the instrument neck at a rapid rate. In a keyboard instrument, such as an organ, suitable mechanical or electrical means must be provided to introduce such vibrato if a natural and pleasing tone quality is to be attained.

It has been suggested to provide organ vibrato by continuously shifting the phase of all of the electrical tone signals. The equipment for accomplishing this result includes a phase shift network or electrical delay line comprising a number of low-pass filter sections and a capacity type pick-up or scanner. The scanner element is motor driven so that it scans back and forth along the delay line.

Electrical signals which are fed into the delay line are shifted in phase by each line section so that at any tap along the line, the phase of the signal is retarded relative to the phase of the signal at the previous tap. The scanning pick-up will thus encounter signals which are increasingly retarded in phase at each successive tap along the line. A shift in phase being equivalent to an instantaneous change in frequency, the continuous change in phase becomes a continuous frequency variation. Since the scanner sweeps from start to end of the line and then back, it alternately raises and lowers the frequency of the output signal, the average frequency remaining equal to the input frequency. The exact amount of frequency shift depends upon the phase shift of the line and the scanning rate. It will be readily seen that this equipment is complex in operation and contains a great many components which add to the cost and maintenance of the equipment.

A feature of the present invention is the provision of an organ vibrato control which eliminates the need for costly electronic components and complicated circuitry.

Another feature of the invention is the provision of an adjustable organ vibrato control which automatically introduces the same amount of vibrato into all of the tone signals.

A further feature of the invention is the method for introducing periodic variations in the instantaneous speed of a tone wheel while maintaining a constant average speed.

These features are realized in one form of the invention which utilizes a plurality of tone wheel generators associated with a common motor-driven shaft. The frequencies of the generated tone signals are dependent upon the speed of rotation of the motor-driven shaft. By applying an intermittent D.C. voltage to the motor driving the shaft, a periodic variation in the speed of the shaft will result. If the period of the intermittent D.C. voltage is chosen to be the -same as the desired vibrato rate, the vibrato will be introduced automatically into the electrical signals generated from the tone wheels. The depth of vibrato or the amount of frequency swing above or below the average or tone frequency, can be controlled by varying the amplitude of the applied D.C. voltage.

This form of the invention is illustrated in the accompanying drawings in which:

FIG. 1 is a diagrammatic illustration of a simple tone producing circuit;

FIG. 2 is a perspective view of the drive mechanism employed in the invention; and

FIG. 3 is a schematic diagram of the organ vibrato control circuit.

Referring now to FIG. 1 of the drawings, a basic tone producing circuit, such as employed in the present invention, comprises a tone wheel 1 mounted on shaft 3. A light source 5, located adjacent tone wheel 1, receives energy from a battery 7 upon operation of switch 9. On the opposite side of tone wheel 1 from the light source 5 is a photoelectric cell .11.

Closing switch 9 causes light source 5 to be activated and shine through tone wheel 1 upon the photoelectric cell 11. By utilizing a tone wheel 1 whose light transmitting characteristics have been modified in a predetermined manner, photoelectric cell 11 can be caused to generate an alternating current signal which represents the desired tone. This signal is fed into a preamplifier 13 and then to a series of formant filters 15, which impart the desired tone characteristics to the signal. The output from the filters 15 is amplified by amplifier 17 and converted into acoustic energy by speak-er 19.

Systems of the type shown in FIG. 1 are well known, and reference may be made to United States Patent No. 2,796,534, issued June 18, 1957, to Richard E. Williams, and United States Patent No. 2,818,761, issued January 7, 8, to Richard E. Williams for a more complete description of the operation of these systems.

The way in which the tone wheel 1 is driven is shownin FIG. 2, which is a perspective view of the driving mechanism. A central driving shaft 21 has a friction disc or gear 23 mounted thereon. A second friction disc or gear 25, which is fixedly mounted on shaft 3, is in engagement with disc 23. Also mounted on shaft 3 is cam 27 which operates a periodic circuit making and breaking means, shown as contacts 29 and 31, for a purpose which will be described later.

Shaft 21 is connected to both a constant speed motor, such as synchronous motor 33, and a self-starting motor, such as shaded pole motor 35. These motors may be contained within a common housing, or separate housings as shown in FIG. 2. Shaded pole motor 35 is used for starting purposes to bring the speed of shaft 21 up to the speed of synchronous motor 33. When this speed is reached, shaded pole motor 35 is tie-energized and the system is run by synchronous motor 33.

The novel vibrato control of the present invention is accomplished by introducing periodically a D.C. voltage into shaded pole motor 35 to produce instantaneous braking effects on driving shaft 21. This periodic instantaneous slowing down of shaft 21, which is made to coincide with the desired vibrato frequency, inherently introduces a vibrato effect into the electrical signal generated by photo cell 11. This will be seen more easily from FIG. 3 which is a schematic diagram of the control circuit.

In FIG. 3, motors 3-3 and 35 are shown connected to a common source of alternating current potential 37. To start the motors, switch 39 is closed and switch 41 is moved from its normally closed position, with arm 43 connected to contact 45, to its normally open position, with arm 43 connected to contact 4-7. In this position, shaded pole motor 35 will provide the necessary starting torque,

and will bring shaft 21 up to the synchronous speed of synchronous motor 33. When this speed is reached, switch 41 is returned to its normally closed position with arm 43 connected to contact 45, and shaded pole motor 35 is thus disconnected from alternating current source 37. Each revolution of shaft 3 causes cam 27 momentarily to close contacts 29 and 31, and with switch 41 in its normally closed position, if either of switches 49 and 51 of the vibrato control 53 is closed, a conductive path will be completed from DC. source 55 through the vibrato control switches, contacts 29, 31, switch 41 and shaded pole motor 35.

Periodically subjecting shaded pole motor 35 to a DC.

potential produces an electromagnetic braking effect which causes instantaneous reductions in speed of driving shaft 21 while allowing the average speed to remain constant. The magnitude of this braking efiect can be controlled by varying the D0. potential applied to motor 35. In FIG. 3 this is accomplished by providing a voltage dividing resistor 57 in conjunction with selective switches 49 and 51 for selecting either the full value of potential source 55 or an attenuated value produced by placing resistor 57' in series with source 55.

The basic principles involved in the electromagnetic braking of motors is well known and it is believed unnecessary to discuss them here. For a more complete understanding of such systems, reference may be made to United States Patent No. 2,419,431, issued April 22, 1947, to Lawrence S. Williams, United States Patent No. 2,445,- 806, issued July 27, 1948, to Frederick D. Snyder, and United States Patent No. 2,767,362, issued October 16,

1956, to William H. Beaubien.

Cam 27, which operates contacts 29 and 31, is shown as being connected directly to shaft 3, which also drives tone wheel 1. This is possible because the speed of shaft 3 happens to fall within the allowable limits for the desired vibrato frequency which usually falls within the range of 4 to 12 cycles per second. If this should not be the case, it will be understood that an alternate gearing arrangement could be provided so that cam 27 would rotate at the desired speed. The transient effects of the intermittent operation of contacts 29 and 31 are minimized by utilizing a conventional filter comprising capacitance 59 and resistance 61.

It will be appreciated that the present invention has provided a simple and economical system for introducing vibrato into the tones of a motor-driven musical instrument. While the system has been described in connection with photoelectric type tone production, the principle of operation is applicable to any system in which a constant speed.

tone wheel generator is employed.

What is claimed is: v 1. In an electric organ, the combination comprising a first shaft having a tone wheel thereon, a second shaft having two motors operatively associated therewith, one of said motors being of constant speed type and the other being of self-starting type, drive means interconnecting said shafts, a source of direct current operatively connected to said self-starting motor, and a periodic circuit making and breaking means in series between said source of direct current and said self-starting motor.

2. In an electric organ, the combination comprising a first shaft having a tone wheel thereon, means associated with said tone wheel for producing an electrical signal upon rotation of said tone wheel, a second shaft having two motors operatively associated therewith, one of said motors being of constant speed type and the other being of self-starting type, drive means interconnecting said shafts, a source of direct current operatively connected to said self-starting motor, and a periodic circuit making and breaking means in series between said source of direct current and said self-starting motor, whereby instantaneous braking effects are produced in said self-starting motor to cause periodic speed variations in the rotation of said tone wheel and introduce vibrato into said electrical signal. 3 3. In an electric organ, the combination comprising a first shaft having a tone wheel thereon, means associated with said tone Wheel for producing an electrical signal upon rotation of said tone wheel, a second shaft having two motors operatively associated therewith, one of said motors being of constant speed type and the other being of self-starting type, drive means interconnecting said shafts, a source of direct current, a source of alternating current, first switch means for connecting said constant speed motor to said source of alternating current, second switch means for selectively connecting said self-starting motor to either said alternating current source or said direct current source, and a periodic circuit making and breaking means in series between said source of direct current and said self-starting motor, whereby instantaneous braking eifects are produced in said self-starting motor to cause periodic speed variations in the rotation of said tone wheel and introduce vibrato into said electrical signal.

References Cited in the file of this patent UNITED STATES PATENTS 1,956,350 Hammond Apr. 24, 1934 2,018,924 Ranger .d Oct. 29, 1935 2,130,251 Richards Sept. 13, 1938 2,513,109 Roth June 27, 1950 2,576,760 Jones et a1 Nov. 27, 1951 2,607,444 Larson Aug. 19, 1952 2,681,584 Williams June 22, 1954 2,746,334 Williams May 22, 1956 

1. IN AN ELECTRIC ORGAN, THE COMBINATION COMPRISING A FIRST SHAFT HAVING A TONE WHEEL THEREON, A SECOND SHAFT HAVING TWO MOTORS OPERATIVELY ASSOCIATED THEREWITH, ONE OF SAID MOTOR BEING OF CONSTANT SPEED TYPE AND THE OTHER BEING OF SELF-STARTING TYPE, DRIVE MEANS INTERCONNECTING SAID SHAFTS, A SOURCE OF DIRECT CURRENT OPERATIVELY CONNECTED TO SAID SELF-STARTING MOTOR, AND A PERIODIC CIRCUIT 